Apolipoprotein B Levels and Altered Lipoprotein Composition in Diabetes

Hyperlipoproteinemia is found in only 25 to 50 per cent of persons with diabetes. However, carbohydrate, lipid and lipoprotein metabolism are so closely related that one would expect some alterations in lipoprotein metabolism in nearly all diabetic subjects. We wondered whether the metabolism of lipoproteins in normoUpemic diabetic patients was normal and whether the metabolism of lipoproteins in subjects with hyperlipoproteinemia and diabetes differed from those without diabetes. As a first approach to these questions, the levels of lipoprotein lipids and apoUpoproteins were determined in ninety-seven diabetics and seventy-two nondiabetics, and lipoprotein compositions were computed. Among those with diabetes, seventy-one were normoUpemic—twelve were type Ila and fourteen were type IV. In each of the diabetic groups, low density and high density lipoproteins were enriched in triglyceride (p < 0.01). These alterations in lipoprotein composition were not accounted for by differences in treatment modality, sex, race, age, or ponderal index. Thus the presence of diabetes itself appears to result in altered low and high density lipoprotein compositions. The mechanism(s) for the changes in the high density lipoproteins is (are) unknown, but in light of present knowledge the presence of triglyceride-enriched LDL could mean that a less dense moiety of low density lipoproteins may be accumulating in diabetic plasma, and this could result from altered rates of turnover of ApoB containing lipoproteins. Of course appropriate studies are needed to confirm this formulation.